1. Field of the Invention
The present invention relates generally to an apparatus and method for communications and particularly to cellular communications.
2. Description of the Related Art
Wireless radio telephone communication technology is well known and has existed for many years. The first true mobile telephone network was introduced in St. Louis, Mo. in 1946. The early mobile telephone systems immediately began experiencing many problems. From a subscriber viewpoint, the initial systems were very inconvenient, requiring much telephone system operator intervention, were relatively expensive and capacity was tiny by the standards of today. Mobility was also a problem.
Cellular telephony was introduced in the U.S. by way of the Advanced Mobile Phone Service (AMPS) during the 1970s and early 1980s. This system is based on FM analog speech transmission. Capacity is increased from previous systems due to frequency re-use among the many cells located within the system. Mobility is provided by the use of hand-off techniques implemented as a mobile station traverses a boundary between cells.
The Global System for Mobile (GSM) communications network was developed and first implemented in Europe in response to a need for even more capacity and compatibility among political and geographic territories. GSM is now an international standard.
GSM is a digital system which offers superior speech quality, low terminal, operational and service costs, an increased level of security (both privacy and fraud prevention), international roaming, support of low-power hand-held terminals and a variety of user services and features. An increase in capacity is achieved due to the use of digital signal processing techniques which allow for bandwidth reduction by elimination of variances inherent in human speech patterns in combination with the frequency re-use schemes of cellular systems.
When a subscriber's mobile station travels from one geographic area (cell, hence the name cellular) to another, the cellular system must track the mobile station movement in order to provide proper service to the subscriber. The cellular system must know where to send a call directed to the subscriber, and must be able to allow a call to continue as a mobile station travels from one cell to another without causing the subscriber the extreme annoyance of dropping the call.
Current mobile systems, including GSM, require a high volume of overhead processing and transmission in order to keep track of user location. Current systems keep track of mobile station location by storing a single permanent copy of a mobile station's identity and related data in a central location, which may be distant from the current location of the mobile station. That centrally stored mobile station data is then sent to the local geographic location of the mobile subscriber each time the mobile station roams to a new area. The mobile station data stored in the old area is then deleted as it is no longer needed. A large amount of processing and transmission resources are thus expended by the need to frequently access and update the mobile station data at the central location.
There exists a need to increase capacity of a network by reducing processing and network management transmission overhead by efficiently locating and tracking the mobile stations located within the boundaries of a cellular network without having to access the centrally stored mobile station data each and every time a mobile station powers up (attaches to the network) or roams from one cell to another, thus freeing up those limited resources to accommodate additional subscriber call volume.